Cosmarium clepsydra var. incrassatum Thérezién (1985:96)

Ramos, Geraldo José Peixoto, Santos, Maria Aparecida Dos & Moura, Carlos Wallace Do Nascimento, 2021, Taxonomic notes on some Cosmarium species (Desmidiaceae, Zygnematophyceae) from Brazil, Phytotaxa 483 (3), pp. 291-299 : 292

Cosmarium clepsydra var. incrassatum Thérezién (1985:96) ( Figs 2 , 16–21 )

Cell dimensions: length 28–30 μm, breadth 21–23 μm, breadth of isthmus 6,5–7 μm.

Material examined:— BRAZIL. Pantanal dos Marimbus,Andaraí, Bahia State. Sample: HUEFS 185370, HUEFS 185390.

Habitat:—It was found on Utricularia foliosa (periphyton).

Note:— This variety, probably endemic to South America , is characterized in having rounded semicells, closed sinus, cell wall locally remarkably thickened and ornamented by scrobicles. Regarding this latter morphological feature, Thérezién reported scrobicles only at the central protuberance and the margins. In the Brazilian specimens, the whole cell wall is ornamented by those scrobiculations, and the cells are slightly longer. The var. incrasstaum is quite rare and till now it was only known to its type locality in French Guiana .

Another Cosmarium taxon which was apparently endemic to that country was recently reported also in the Marimbus, Brazil: Cosmarium anisochondrum var. isthmolatum Thérézien (1985:85) ( Ramos et al. 2021). Overall, there are other rare desmids co-occurring in French Guiana and Brazil, especially in the Chapada Diamantina region, such as Euastrum subcyclopicum var. elongatum Thérézien (1985: 82) ( Ramos et al. 2019). However, more studies are recommended to investigate such similarity between the desmid flora of those two countries.

Figures

FIGURES 1–8. Line drawings. 1. Cosmarium boeckii var.areolatum 2. C. clepsydra var. incrassatum 3. C. heptangulare 4. C. kanetsunae 5. C. pygmaeum 6. C. trinodulum 7. C. trinodulum var. brasiliense 8. C. trinodulum var. pilgeri.

FIGURES 9–32. LM and SEM. 9–15. Cosmarium boeckii var. areolatum: LM (9–12), SEM (15), frontal view (9, 10, 15), lateral view (11, 12), apical view (13, 14), 16–21. C. clepsydra var. incrassatum: frontal view (16–19), lateral view (20), apical view (21), 22–26. C. heptangulare: LM (22–25), SEM (26), frontal view (22–23, 26), lateral view (24), apical view (25), 27–32. C. kanetsunae: frontal view (27–28), lateral view (29, 30), apical view (31, 32). Scale bar: 10 μm, except Fig. 15 (5 μm).